Cloramines are now the purifier of choice for most of our water agencies because it has no aroma.  Unlike clorine, cloramines do not break down and evaporate quickly.  Instead the clorine evaporates out of the molecule leaving ammonia residue in the soil.  Ammonia is harmful to all life which is why we cannot top up our fish ponds with tapwater without using a modifier to get rid of the ammonia.  Likewise, ammonia may harm soil bacteria and that is another good reason to irrigate your garden as little as possible.